Field of the Invention
The present disclosure relates to an image sensor, and in particular to an imaging device capable of performing a phase detection autofocus function in a low-light environment.
Description of the Related Art
In recent years, phase detection autofocus (PDAF) technology has been introduced to imaging products, such as DSLR cameras and mobile phone cameras. Phase detection is achieved by dividing the incoming light into a pair of images and comparing them. Specifically, one conventional method is to have two green pixels with opaque materials covering half of the area of their apertures. The differential signal of the two pixels is calculated to find if the object is in a front focus or back focus position. This gives the direction and an estimate of the required amount of focus mechanism movement. However, the structure cannot perform the PDAF function under low-light conditions, because the collected signals for phase detection are too weak.
On the other hand, in the field of surveillance, an infrared pixel for near-infrared detection is arranged in the image sensor array to replace one green pixel in the Bayer pattern. When the environment is too dark, the surveillance camera uses an assistant infrared light source to irradiate near-infrared light to the front of the surveillance camera, and the infrared pixel detects the near-infrared light reflected by the object in front of the surveillance camera. In this way, imaging products can perform imaging in a low-light environment. However, the existing imaging product embedded with infrared pixels still has no way of performing the PDAF function. In this regard, the purpose of the disclosure is to provide an image sensor and an imaging device using the same capable of performing the PDAF function in a low-light environment.